The present invention relates to a process for producing xcfx89-mercaptoalkylpyridine.
xcfx89-Mercaptoalkylpyridine such as 2-(2-mercaptoethyl)pyridine, 4-(2-mercaptoethyl)pyridine and the like are industrially useful compounds as an additive of chelating catalysts for producing bisphenol A; intermediates for medical supplies or agricultural chemicals; and the like.
Conventionally, as the method for producing xcfx89-mercaptoalkylpyridines, there is reported, for example, a method of reacting 2-vinylpyridine with hydrogen sulfide to produce 2-(2-mercaptoethyl)pyridine in a yield of 23% (P. S. K. Chia et al., Aust. J. Chem., 19, 1835 (1966) and R. B. Thompson et al., Industrial and Engineering Chemistry, 44, 1659 (1952)).
An object of the present invention is to provide a process for producing xcfx89-mercaptoalkylpyridines in high yield even if industrially easily available hydrogen sulfide is used.
The present invention relates to the followings.
 less than 1 greater than  A process for producing xcfx89-mercaptoalkylpyridine of the formula (II) 
wherein R1 and R2 each independently represent hydrogen or methyl, and
n represents an integer of 0 to 2,
comprising reacting pyridine compound of the formula (I) 
wherein R1, R2 and n have the same meanings described above, and hydrogen sulfide in the presence of tertiary amine, which is hereinafter referred to as xe2x80x9cthe present processxe2x80x9d.
 less than 2 greater than  The process according to  less than 1 greater than  wherein the tertiary amine is at least one tertiary amine compound selected from the group consisting of the following (A) to (C): 
wherein R21, R22 and R23 each independently represent alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 12 carbon atoms or aromatic hydrocarbon group having 6 to 12 carbon atoms and at least one hydrogen on the alkyl, cycloalkyl or aromatic hydrocarbon group may be substituted by amino, N-alkylamino having 1 to 8 carbon atoms, N,N-diakylamino having 2 to 16 carbon atoms or hydroxy. 
wherein R24 represents alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 12 carbon atoms or aromatic hydrocarbon group having 6 to 12 carbon atoms, m represents an integer of 0 to 8, and at least one hydrogen atom on xe2x80x94CH2xe2x80x94 constituting a ring or on R24 may be substituted by amino group, N-alkylamino group having 1 to 8 carbon atoms, N,N-dialkylamino group having 2 to 16 carbon atoms or hydroxyl and one or two xe2x80x94CH2xe2x80x94 constituting a ring may be substituted by xe2x80x94NHxe2x80x94 or xe2x80x94Oxe2x80x94.
(C): Aromatic nitrogen-containing heterocyclic compound wherein at least one hydrogen may be substituted by alkyl having 1 to 8 carbon atoms and at least one hydrogen on the alkyl may be substitutede by amino, N-alkylamino having 1 to 8 carbon atoms or N,N-dialkylamino having 2 to 16 carbon atoms.
 less than 3 greater than  The process according to  less than 1 greater than  or  less than 2 greater than  wherein the pyridine compound of the formula (I) is at least one kind selected from the group consisting of 4-vinylpyridine and 2-vinylpydirine.
 less than 4 greater than  The process according to any one of  less than 1 greater than  to  less than 3 greater than  wherein the tertiary amine is at least one compound selected from the group consisting of tertiary amine of the following formula (1), tertiary amine of the following formula (2), tertiary amine of the following formula (5) and tertiary amine of the following formula (6):
Tertiary amine of the formula (1) 
wherein R3 to R1 each independently represent alkyl having 1 to 8 carbon atoms or cycloalkyl having 4 to 12 carbon atoms.
Tertiary amine of the formula (2) 
wherein R6 to R9 each independently represent alkyl having 1 to 8 carbon atoms or a cycloalkyl having 4 to 12 carbon atoms, p represents an integer of 1 to 8.
Tertiary amine of the formula (5) 
wherein R13 and R14 each independently represent alkyl having 1 to 8 carbon atoms or cycloalkyl having 4 to 12 carbon atoms, and xcfx861 represents aromatic hydrocarbon group.
Tertiary amine of the formula (6) 
wherein R15 represents alkyl having 1 to 8 carbon atoms or cycloalkyl having 4 to 12 carbon atoms, and xcfx862 and xcfx863 each independently represent aromatic hydrocarbon group.
 less than 5 greater than  The process according to any one of  less than 1 greater than  to  less than 4 greater than  wherein tertiary amine and pyridine (I) are sequentially mixed with hydrogen sulfide previously filled in a reaction.
The present invention will be illustrated in detail below.
In the pyridine compound of the formula (I), which is hereinafter referred to as xe2x80x9cpyridine (I)xe2x80x9d, the compound wherein n is 0 is preferable, and pyridine (I) in which both of R1 and R2 represent hydrogen and n is 0 is particularly preferable, and among others, 2-vinylpyridine and 4-vinylpyridine are suitable.
Polymerization inhibitors such as hydroquinones, catechols and the like may be contained usually in an amount of about 0.01 to 0.5% by weight based on pyridine (I), which is sometimes added for deterioration inhibitor of pyridine (I) when stored. It is however recommended that pyridine (I) is purified by simple distillation before the present process.
As hydrogen sulfide used in the present process, that in the form of solution which is dissolved in a solvent such as water, carbon disulfide, methylene chloride and the like may be used, and usually, commercially available compressed hydrogen sulfide contained in a cylinder, gaseous hydrogen sulfide produced, for example, in a factory, and the like, are used as they are. As the specific hydrogen sulfide use method, there are exemplified a method in which hydrogen sulfide is previously introduced into a reaction vessel, then, pyridine (I) and tertiary amine are mixed; a method in which hydrogen sulfide is blown through an introduction tube or the like into a reaction vessel containing mixture of pyridine (I) and tertiary amine; a method in which pyridine (I), tertiary amine and hydrogen sulfide are introduced into a reaction vessel, and the like. For performing the reaction efficiently in use of hydrogen sulfide, the reaction vessel may be sealed, or if necessary, may be pressurized.
The amount of hydrogen sulfide is usually more than 1 mol per 1 mol of pyridine (I), and from the economical standpoint, preferably less than 30 mol. When the reaction is conducted in a sealed vessel, the amount of hydrogen sulfide is usually more than 1 mol per 1 mol of pyridine (I), and from the economical standpoint, preferably less than 10 mol.
The tertiary amine used in the present invention is an amine compound having a nitrogen atom whose three bonds connect with carbon atoms.
Preferred examples of the tertiary amine include at least one organic amine compound selected from the group consisting of the following (A) to (C).
(A): Amine comppund of the formula (a) 
wherein R21, R22 and R23 each independently represent alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 12 carbon atoms or aromatic hydrocarbon group having 6 to 12 carbon atoms and at least one hydrogen on the alkyl, cycloalkyl or aromatic hydrocarbon group may be substituted by amino, N-alkylamino having 1 to 8 carbon atoms, N,N-dialkylamino having 2 to 16 carbon atoms or hydroxy.
(B): Alicyclic amine of the formula (b) 
wherein R24 represents alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 12 carbon atoms or aromatic hydrocarbon group having 6 to 12 carbon atoms, m represents an integer of 0 to 8, at least one hydrogen atom on xe2x80x94CH2xe2x80x94 constituting a ring or on R24 may be substituted by amino group, N-alkylamino group having 1 to 8 carbon atoms, N,N-dialkylamino group having 2 to 16 carbon atoms or hydroxyl, and one or two xe2x80x94CH2xe2x80x94 constituting a ring may be substituted by xe2x80x94NHxe2x80x94 or xe2x80x94Oxe2x80x94.
(C): Aromatic nitrogen-containing heterocyclic compound wherein at least one hydrogen may be substituted by alkyl having 1 to 8 carbon atoms and at least one hydrogen on the alkyl may be substitutede by amino, N-alkylamino having 1 to 8 carbon atoms or N,N-dialkylamino having 2 to 16 carbon atoms.
Examples of alkyl group having 1 to 8 carbon atoms in (A), (B) or (C) include methyl, ethyl, butyl and the like. Examples of cycloalkyl having 4 to 12 carbon atoms in (A) include cyclopentyl, cyclohexyl and the like.
Examples of aromatic hydrocarbon group having 6 to 12 carbon atoms in (A) include phenyl, benzyl and the like.
Examples of (A) include tertiary amine having a nitrogen atom bonded to an aromatic hydrocarbon group; weak basic ion exchanged resin having xe2x80x94CH2N(CH3)2 on a styrene-divinylbenzene skeleton; and the like.
As the tertiary amines having a nitrogen atom bonded to three alkyl groups, for example, tertiary amines of the following formulae (1) to (4), and the like are listed. 
In the formula (1), R3 to R5 each independently represent alkyl having 1 to 8 carbon atoms or cycloalkyl having 4 to 12 carbon atoms.
Specific examples of the tertiary amine of the formula (1) include trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, diisopropylethylamine, and the like. 
In the formula (2), R6 to R9 each independently represent alkyl having 1 to 8 carbon atoms or a cycloalkyl having 4 to 12 carbon atoms. p represents an integer of 1 to 8. Specific examples of the tertiary amine of the formula (2) include N,N,Nxe2x80x2,Nxe2x80x2-tetramethyldiaminomethane, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethyl-1,3-propanediamine and the like. 
In the formulae (3) and (4), R10 to R12 each independently represent alkyl having 1 to 8 carbon atoms or cycloalkyl having 4 to 12 carbon atoms. q and r each independently represent an integer of 1 to 4.
As the tertiary amine of the formula (3), N,N-diethylethanolamine is exemplified, and as the tertiary amine of the formula (4), N-methyldiethanolamine is exemplified.
As the tertiary amines having a nitrogen atom bonded to an aromatic hydrocarbon group, for example, tertiary amines of the following formulae (5) and (6), and the like are listed. 
Wherein, R13 to R15 each independently represent alkyl having 1 to 8 carbon atoms or cycloalkyl having 4 to 12 carbon atoms. xcfx861 to xcfx863 each independently represent aromatic hydrocarbon group.
Specific examples of the tertiary amine of the formula (5) include N,N-dimethylaniline, N,N-diethylaniline and the like. Specific examples of the tertiary amine of the formula (6) include diphenylmethylamine, diphenylethylamine and the like.
Examples of (B) the alicyclic amines of the formula (b) include alicyclic tertiary amines such as bis(aminopropyl)piperazine, N-methylpiperazine, 1-(2-aminoethyl)piperazine, (hydroxyethyl)piperazine, N-methylpiperazine, N-methylmorpholine, N-ethylmorpholine, N-(3-aminopropyl)morpholine, 1,4-diazabicyclo[2,2,2]octane and the like.
Examples of (C) the aromatic nitrogen-containing heterocyclic compounds in which at least one hydrogen atom may be substituted by alkyl group include pyridine, xcex1-picoline, xcex3-picoline, lutidine, 2-propylpyridine, 4-pyrrolidinopyridine, 4-piperidinopyridine, o-phenanthroline and the like.
As the tertiary amine in the present invention, different two kinds or more of tertiary amines may be used.
As the tertiary amine, preferable are, from the standpoint of the yield of xcfx89-mercaptoalkylpyridine of the formura (II), which is hereinafter referred to as xcfx89-mercaptoalkylpyridine (II), tertiary amines belonging to the above-mentioned (A) and (B), and among them, tertiary amines of the formulae (1), (2), (5) and (6) are more preferable and tertiary amines of the formulae (1) and (2) are particularly preferable.
The amount of the tertiary amine in the present invention may advantageously be 0.005 mol or more per 1 mol of pyridine (I), and the tertiary amine may be used as a solvent.
Specific use amount of the tertiary amine is, in the case of separate use of a solvent, usually from about 0.001 to 1 mol per mol of pyridine (I), and in the case of use as a solvent, usually from about 1 to 100 mol per 1 mol of pyridine (I).
In the present process, a solvent may be used, or production may be effected without using a solvent.
As the solvent, exemplified are organic solvents such as tetrahydrofuran, diethyl ether, methanol, ethanol, isopropanol, acetonitrile, xylene, toluene, benzene, dimethylformamide, acetone, ethyl acetate, hexane, dichloromethane, chloroform and the like.
As the solvent, two kinds or more of solvents may be used.
The present invention is a process for producing xcfx89-mercaptoalkylpyridine (II) comprising reacting pyridine (I) with hydrogen sulfide in the presence of the tertiary amine.
Specifically listed are (i) a method in which hydrogen sulfide is introduced into solution containing the tertiary amine, pyridine (I), and if necessary, solvent; (ii) a method in which hydrogen sulfide is introduced into solution containing the tertiary amine, and if necessary, a solvent, then, pyridine (I) is mixed; (iii) a method in which tertiary amine and pyridine (I) are sequentially mixed with hydrogen sulfide previously filled in a reaction vessel; (iv) a method in which pyridine (I) and tertiary amine are mixed sequentially or in one time with hydrogen sulfide previously filled in a reaction vessel, (v) a method in which the tertiary amine, pyridine (I) and hydrogen sulfide are mixed at one time in a reaction vessel, and the like.
In the process of the present invention, methods of adding pyridine (I) into a reaction vessel previously filled with hydrogen sulfide such as the methods (ii) and (iii) are preferable since production of by-products such as sulfides described later, tends to be suppressed and particularly, the method (iii) is particularly suitable.
The pressure after introduction of hydrogen sulfide (gage pressure, namely, pressure difference based on atmospheric pressure) is from 0.1 to 1.5 MPa, preferably from 0.2 to 1 MPa. The form of hydrogen sulfide in a reaction vessel may be gas or liquid. In pressurizing, inert gas such as nitrogen, helium and the like may be used to control pressure. Further, hydrogen sulfide remaining after completion of the reaction may be transferred to other vessel and re-used in the present process.
The reaction temperature in the present process is usually from about xe2x88x9240 to 100xc2x0 C., preferably from about xe2x88x9230 to 60xc2x0 C. When the reaction temperature is xe2x88x9240xc2x0 C. or higher, the reaction speed tends to increase, and when 100xc2x0 C. or lower, production of by-products of sulfides such as the compound of the following formula (III) tends to be suppressed. 
In the formula (III), R1, R2 and n have the same meanings as above.
The reaction time is usually from about 0.1 to 20 hours, though changing depending on the amount ratio of pyridine (I), the tertiary amine and hydrogen sulfide, mixing method, reaction temperature and the like.
The tertiary amine may be removed by concentration under reduced pressure, washing with water, and the like from the resulted reaction mixture to obtain xcfx89-mercaptoalkylpyridine (II). xcfx89-Mercaptoalkylpyridines (II) thus obtained may be used for further reaction without any treatment as a intermediate of, for example, catalyst. Alternatively, the form of xcfx89-mercaptoalkylpyridine (III) may be changed to aqueous solution of the salt thereof by using inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like, organic acid such as acetic acid, citric acid and the like.
Further purification can be performed by distilation or by recrystallization of, for example, hydrochloride salt thereof.